Bioenergy deployment offers significant potential for climate change mitigation, but also carries considerable risks. In this review, we bring together perspectives of various communities involved in the research and regulation of bioenergy deployment in the context of climate change mitigation: Land‐use and energy experts, land‐use and integrated assessment modelers, human geographers, ecosystem researchers, climate scientists and two different strands of life‐cycle assessment experts. We summarize technological options, outline the state‐of‐the‐art knowledge on various climate effects, provide an update on estimates of technical resource potential and comprehensively identify sustainability effects. Cellulosic feedstocks, increased end‐use efficiency, improved land carbon‐stock management and residue use, and, when fully developed,BECCSappear as the most promising options, depending on development costs, implementation, learning, and risk management. Combined heat and power, efficient biomass cookstoves and small‐scale power generation for rural areas can help to promote energy access and sustainable development, along with reduced emissions. We estimate the sustainable technical potential as up to 100 EJ: high agreement; 100–300 EJ: medium agreement; above 300 EJ: low agreement. Stabilization scenarios indicate that bioenergy may supply from 10 to 245 EJ yr⁻¹to global primary energy supply by 2050. Models indicate that, if technological and governance preconditions are met, large‐scale deployment (>200 EJ), together withBECCS, could help to keep global warming below 2° degrees of preindustrial levels; but such high deployment of land‐intensive bioenergy feedstocks could also lead to detrimental climate effects, negatively impact ecosystems, biodiversity and livelihoods. The integration of bioenergy systems into agriculture and forest landscapes can improve land and water use efficiency and help address concerns about environmental impacts. We conclude that the high variability in pathways, uncertainties in technological development and ambiguity in political decision render forecasts on deployment levels and climate effects very difficult. However, uncertainty about projections should not preclude pursuing beneficial bioenergy options.

This paper revisits the theoretical concepts of lock-in mechanisms to analyse transitionprocesses in energy production and road transportation in the Nordic countries, focussingon three technology platforms: advanced biofuels, e-mobility and hydrogen and fuel cellelectrical vehicles. The paper is based on a comparative analysis of case studies.The main lock-in mechanisms analysed are learning effects, economies of scale,economies of scope, network externalities, informational increasing returns, technologi-cal interrelatedness, collective action, institutional learning effects and the differentiationof power.We show that very different path dependencies have been reinforced by the lock-inmechanisms. Hence, the characteristics of existing regimes set the preconditions for thedevelopment of new transition pathways. The incumbent socio-technical regime is not justfossil-based, but may also include mature niches specialised in the exploitation of renew-able sources. This implies a need to distinguish between lock-in mechanisms favouringthe old fossil-based regime, well-established (mature) renewable energy niches, or newpathways